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Old 05-31-2010, 12:21 PM   #1
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Tire pressures

On another thread I mentioned going to "E" rated tires at 80 psi (Maxxis 8008), because of all the negative stories I heard about the Goodyears. Someone made a point that 80 psi would cause structural damage to my 28' International. Does it hurt to run the air pressure less than maximum without any negative results like 65-70 psi? thanks
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Old 05-31-2010, 12:31 PM   #2
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I went with 16" eagle alloy wheels and the 16" BF Goodrich Commercial LT tire a few years ago on my 1976 31' Sovereign. The max psi for this tire is 80 lbs. I have always run them at about 50 psi. The trailer rides great and after about 20,000 miles the tires look great with no cupping or unusual ware.

Check on the Maxxis web site for the load rating at lower psi than the max 80 lbs. Then adjust accordingly.

Don
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Old 05-31-2010, 12:52 PM   #3
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Quote:
Originally Posted by BCMC27 View Post
On another thread I mentioned going to "E" rated tires at 80 psi (Maxxis 8008), because of all the negative stories I heard about the Goodyears. Someone made a point that 80 psi would cause structural damage to my 28' International. Does it hurt to run the air pressure less than maximum without any negative results like 65-70 psi? thanks
Go out to your car and check the recommended inflation from the owner's manual or the placard. Now check the maximum inflation on your tires' sidewalls. They are not the same.

Maximum inflation is for maximum load. Check out this website on reading tire wear. With new tires you don't see tire wear comparisons as much as we did in the past. However, notice that the first example is for Over Inflation.

Proper inflation results in even temperatures and wear across the tread of the tire. It is directly related to the load on the tire and is only achieved for maximum inflation with the maximum load on the tire.
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Old 05-31-2010, 01:43 PM   #4
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Originally Posted by vswingfield View Post
Go out to your car and check the recommended inflation from the owner's manual or the placard. Now check the maximum inflation on your tires' sidewalls. They are not the same.

Maximum inflation is for maximum load. Check out this website on reading tire wear. With new tires you don't see tire wear comparisons as much as we did in the past. However, notice that the first example is for Over Inflation.

Proper inflation results in even temperatures and wear across the tread of the tire. It is directly related to the load on the tire and is only achieved for maximum inflation with the maximum load on the tire.

Most cars and especially trucks the load on the road varies a lot. One driver and no gear is a light load and what the tire inflation guide on a car is set up for. Also a lower pressure in the past would give a smoother or softer ride. Consumers liked this kind of ride.

Fill the trunk and click all of the seat belts and you have just bumped the load by 4 to 6 six times the previous example. In a truck it gets much more dramatic. And you need to know the vehicle design is a balance between the max designed load and retail cost to the consumer.

Travel trailers .... the load is usually static. Meaning the load on the road is about the same plus or minus a couple hundred pounds. The design for this is such that the window is much smaller for things needed in the running gear. Speaking of tires the traler manufacture gets a tire that at max inflation handles the max designed load for the trailer. Because more of a tire costs more and going to market with a tire that can handle more at max pressure than needed is a waste. (or more expensive) Consumers being the one that would rather pay less for something than more this only makes sense.

Now you come along and buy a tire that can handle way more than the trailer was designed to carry. Lowering the inflation is the way to go. Because at lower inflation pressures the designed level of load for the tire is less. And the trie is softer and rides softer.

At what point do you lower the pressure in the tire to meet the load? That is a tire manufacturer question. And you need to know the weight of your towed load. So weighing your towed load is needed as well.

>>>>>>>>>>>>>Action
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Old 05-31-2010, 02:36 PM   #5
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Originally Posted by Action View Post
Most cars and especially trucks the load on the road varies a lot. One driver and no gear is a light load and what the tire inflation guide on a car is set up for. Also a lower pressure in the past would give a smoother or softer ride. Consumers liked this kind of ride.

Fill the trunk and click all of the seat belts and you have just bumped the load by 4 to 6 six times the previous example. In a truck it gets much more dramatic. And you need to know the vehicle design is a balance between the max designed load and retail cost to the consumer.

Travel trailers .... the load is usually static. Meaning the load on the road is about the same plus or minus a couple hundred pounds. The design for this is such that the window is much smaller for things needed in the running gear. Speaking of tires the traler manufacture gets a tire that at max inflation handles the max designed load for the trailer. Because more of a tire costs more and going to market with a tire that can handle more at max pressure than needed is a waste. (or more expensive) Consumers being the one that would rather pay less for something than more this only makes sense.

Now you come along and buy a tire that can handle way more than the trailer was designed to carry. Lowering the inflation is the way to go. Because at lower inflation pressures the designed level of load for the tire is less. And the trie is softer and rides softer.

At what point do you lower the pressure in the tire to meet the load? That is a tire manufacturer question. And you need to know the weight of your towed load. So weighing your towed load is needed as well.

>>>>>>>>>>>>>Action
Well Said!

Nice expansion on my post.
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Old 05-31-2010, 04:11 PM   #6
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Take it, Take it, to the limit, limit

Quote:
Originally Posted by adonh View Post
...Check on the Maxxis web site for the load rating at lower psi than the max 80 lbs. Then adjust accordingly.
Quote:
Originally Posted by vswingfield
...Proper inflation results in even temperatures and wear across the tread of the tire. It is directly related to the load on the tire and is only achieved for maximum inflation with the maximum load on the tire...
I had EXACTLY the same observations until 2airishuman cerebrally beat me up about adjusting tire pressures in this post.

But after thinking about it, I decided that a tandem axle trailer's life is significantly different than an automobile's. Tire sidewall stresses encountered backing a trailer up at an almost 90 degree angle are NOTHING a car tire will ever see.

We just returned from a 1000 mile round-trip journey to Tybee Island Georgia with my Overlander sporting brand-new Goodyear Marathon load range C tires pumped up to their maximum pressure of 50 psig. These tires replaced seven-year-old bias-ply tires run at their maximum pressure of 45 psig.

I was agog at every stop at how much better radials are than bias-ply tires. NOTHING moved inside the Airstream. In fact, on the trip home, we pulled over for a potty break in a remote area, and Kim told me a brush had been left out on the bathroom sink (my Overlander is a rear-bath model). In days of old, NOTHING would have stayed put on an elevated surface that far aft of the axles.

In conclusion, I now endorse the manufacturers's maximum recommended inflation pressure for trailer tires. But, I also HIGHLY recommend going with the load range tires which correspond to your Airstream's weight. Read the two links listed above if you want more insight into why boosting the load range is not necessarily a good thing.

Tom
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Old 05-31-2010, 04:59 PM   #7
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I like radials because they pull better. However I am kind of a cheap ...... fill in the blank. (and my wife will back up that judgement) So I only buy to meet the need. OK meet and then exceed by a very small margin. You will never see a set of tires on one of my towables that isn't at max pressure.

If i bought the tires they don't exceed the load capacity by more than 125% at worst case and it is more like 110% of the max load. In the case of my boat trailer it is more like 102% because of what is available in the rim size. I am just not in to buying more tire than what is required. I would rather buy fuel and go some where.

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Old 05-31-2010, 05:07 PM   #8
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Huh?

Quote:
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..If i bought the tires they don't exceed the load capacity by more than 125% at worst case and it is more like 110% of the max load. In the case of my boat trailer it is more like 102% because of what is available in the rim size. I am just not in to buying more tire than what is required. I would rather buy fuel and go some where...
I seriously do not follow what you are saying.

If nothing else, this is an Airstream forum, not a boat forum.

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Old 05-31-2010, 05:32 PM   #9
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As far as tires go boat trailers and travel trailers it is all the same. Don;t get hung up on the trailer type.

The original poster is talking about buying "E" rated tires and dialing down the pressure because the load capacity is so much greater than what is needed for the actual load towed.

My point in the post I made is why buy a tire with a load range that far exceeds the load capacity of the trailer? By doing so, you then need to back off from the max pressure of the tire since the tire would be way over capacity from the towed load. Not doing so means the tire ride will be too stiff.

Using the above example in post # 1 -
Let's say the 28' trailer max loaded weight will be 7000#'s
And a Load range "D" tire in the acceptable size is rated at 1880 #'s each
And a load rage "E tire in the acceptable size is rated at 2200 #'s each

The Ds are max rated for 7520 #'s and the more expensive Es are rated for 8800 #'s. And to get the E rated tire to work you would have to dial down the pressure from 80PSI to 65PSI. Why pay for E range tires that at max pressure are 126% greater than needed capacity for the load towed?

In my opinion it is a waste of money and effort to go there and dial down the pressure so you don't beat the trailer up.


>>>>>>>>>>>>>>>>Action

(BTW the above figures are only meant as an example and do not represent any actual data for any actual tire)
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Old 05-31-2010, 05:37 PM   #10
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Fair enough

Quote:
Originally Posted by Action View Post
... My point in the post I made is why buy a tire with a load range that far exceeds the load capacity of the trailer? ...
I now understand your point, and I agree. Thanks for the clarification.

Tom
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